Interactions between two strains of lactic acid bacteria and Laetiporus sulphureus strain FH24 and FH319, and Wolfiporia cocos strain FH9 mycelium

This study investigates the interactions between two strains of lactic acid bacteria (LAB; Lactococcus lactis subsp. lactis and Leuconostoc mesenteroides) and the mycelium of two edible fungal species of the Polyporaceae; Laetiporus sulphureus and Wolfiporia cocos. Co-inoculation of LAB and mycelia on agar plates increased the growth of both fungal strains. Using different liquid- and solid-state fermentation techniques, combined with HPLC and GC-MS analyses, we discovered that co-fermentation of LAB with the fungi promoted fungal growth and induced morphological changes in the mycelia. Seven volatile compounds were found to differ between samples of monocultures and co-cultures. Wolfipora cocos (FH9) seemed to cause metabolic changes in L. lactis, in which the production of acetoin and acetate was reduced. Linalool was tested as the inducer compound and high concentrations inhibited bacterial growth. A lower concentration of linalool resulted in no production of acetic acid by L. lactis NFICC188, confirming results from GC-MS analysis. The results demonstrated that co-culturing Wolfipora cocos (FH9) or Laetiporus sulphureus (FH24) with the two LAB strains on agar plates could increase the yield of fungal biomass by 3.3 times on average, 6 days after inoculation. In comparison, agar plates containing commercial acids increased the fungal yield with an average of 3.7 times, 6 days after inoculation. For liquid cultures, the increase in mycelial biomass was generally higher for co-cultures with Lactococcus lactis strain NFICC188 than for pre-acidified media. This could be an important future strategy for growing L. sulphureus or W. cocos mycelia for medicine or human consumption.